Dual lever mechanisms and method of calibration thereof

ABSTRACT

Dual lever mechanisms especially well suited for use in a combination control device for gas burner apparatus having a reset operator, an electromagnetic holding device and a safety valve member, the dual lever mechanisms including a first lever having one arm actuated by the reset operator, a second arm engaging the magnet armature and a third arm spaced from the second arm and movable into engagement with a second lever for the safety valve member and pivoted in common with the first lever; lost motion is provided between the first and second levers such that the second lever is not engaged by the third arm of the first lever until the final movement of the reset operator whereupon the valve member is lifted from its seat a slight amount thereby permitting the pressure differential experienced across the valve to be balanced. A torsion spring for the second lever thereafter moves the second lever so as to fully open the safety valve.

United States Patent [1 1 Katchka [11] 3,747,617 [451 July 24,1973

[ DUAL LEVER MECHANISMS AND METHOD Primary Examiner-Martin P. SchwadronOF CALIBRATION THEREOF Assistant Examiner-Richard Gerard [75] Inventor:Jay R. Katchka, Long Beach, Calif. AtmmeyBrenner O Bnen & Guay [73]Assignee: Robertshaw Controls Company,

Richmond, Va. [57] ABSTRACT Filed: J y 4, 1971 Dual lever mechanismsespecially well suited for use in [21] APPL No: 162,556 a combinationcontrol device for gas burner apparatus having a reset operator, anelectromagnetic holding device and a safety valve member, the dual levermecha- U.S. v. nisms including a first lever having one arm actuated251/78, 251/223, 431/54 the reset operator, a second arm engaging themagnet Int. CL n armature and a arm spaced from the econd arm Field ofSearch 251/75, and movable into engagement with a second lever for 228;137/65, 66 the safety valve member and pivoted in common with v thefirst lever; lost motion is provided between the first References Citedand second levers such that the second lever is not en- UNITED STATESPATENTS gaged by the third arm of the first lever until the final2,496,638 2/1950 Ray 137/66 movement of the reset Operator whereupon thevalve 2, 15 034 12 1957 Kautz 7 5 member is lifted from its seat aslight amount thereby 2,817,973 12/1957 Glickman 137/65 X permitting thepressure differential experienced across ,831, 9 Cu et 3 /6 the valve tobe balanced. A torsion spring for the sec- 3,5l3,873 Graham et al137/495 0nd lever thcreafte moves the second lever so as to fully openthe safety valve.

3 Claims, 9 Drawing Figures I0 I I 50 56 l 2 s? 40 5 38 a4 54 68 a l l4l2 6O I l P 72 32 ll a 28 N 30 8O i i l 26 ll 1 22 til ll IZQI PatentedJuly 24, 1973 3 Sheets-Sheet l IiNVENTOR,

Jay R. KOTChkCI BY 7 ATTORNEYS Patented July 24, 1973 3,747,617

3 Sheets-Sheet 2 INVENTOR,

Jay R. Korchko BY W WW ATTORNEYS Patented July 24,1973 3,747,617

3 Sheets-Sheet 5 INVENTOR,

Jay R. KCITChkCl ATTORNEYS DUAL LEVER MECHANISMS AND METHOD OFCALIBRATION THEREOF BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to lever mechanisms and moreparticularly to a dual lever mechanism for a safety valve member in agas burner control device which prevents damage to the valve assemblyduring operation.

2. Description of the Prior Art The prior art, as exemplified by U.S.Pats. No. 2,815,034, No. 2,817,973 and No. 2,831,491, is generallycognizant of dual lever assemblies for control devices used inconnection with burner apparatus to provide sequential operation of twoloads upon manual resetting of the control. As exemplified by the abovepatents, the prior art dual lever assemblies have been used typically tosequence the opening of a pilot valve and a separate main flow valve forsafety purposes. With the advent of improved combination control deviceswhich utilize only a single safety valve, as illustrated by U.S. Pat.No. 3,513,873, the need for such prior art lever mechanisms for the mostpart has been obviated; however, it has been found that the use ofexcessive force in resetting these single safety valve control deviceshas often caused damage to the valve, the valve lever or theelectromagnetic holding assembly associated therewith. A practicalsolution to this problem, either through the use of a conventional duallever mechanism or any other technique, heretofore has not been realizedand the lack of such a feature has proven to be a distinct disadvantageespecially in view of resulting maintenance and repair costs.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to actuate two loads sequentially by means of a dual levermechanism which exhibits lost motion so as to isolate one of the loadsfrom excessive actuating force.

The present invention is summarized in a dual lever mechanism includinga shaft, a first lever intermediately disposed on the shaft and havingafirst arm extending from one end thereof and second and third spacedarms extending in a direction opposite that of the first arm from theother end thereof, and a second lever journaled for rotation at one endon the shaft and having a portion thereof disposed between the secondand third arms of the first lever for selective engagement by the secondand third arms whereby the first and second levers exhibit lost motioncoupling therebetween.

The present invention has another object in that a safety valve in a gascontrol device is only slightly opened in response to actuation of amanual operator and thereafter is completely opened independently of themanual operator by a biasing spring.

A further object of this invention is to transmit the full movement of areset plunger to a resettable holding device and only a terminal portionof such movement to a safetyvalve member associated with the holdingdevice.

Another object of the present invention is to easily and preciselycalibrate a dual lever mechanism for a safety valve in a control deviceused in connection with burner apparatus.

Other objects and advantages of the present invention will becomeapparent from the following description of the preferred embodimentswhen taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view ofburner control apparatus embodying a dual lever mechanism according tothe present invention showing the lever mechanism in a first operativeposition;

FIG. 2 is a partial section of the apparatus of FIG. 1 showing the duallever mechanism in a second operative position;

FIG. 3 is a partial section similar to FIG. 2 showing the dual levermechanism in a third operative position;

FIG. 4 is a partial section similar to FIG. 2 showing the dual levermechanism in a fourth operative position;

FIGS. 5 and 6 are partial sections similar to FIG. 2 illustrative of amethod of calibrating the dual lever mechanisms according to the presentinvention;

FIG. 7 is a partial exploded view of a modification of the dual levermechanism of FIG. 1;

FIG. 8 is a perspective view of the dual lever mechanism of FIG. 7 inone operative position; and

FIG. 9 is a partial perspective view similar to FIG. 8 showing the duallever mechanism of FIG. 7 in another operative position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While the present invention isapplicable to various types of control assemblies, it will be describedin connection with a combination control device for burner apparatus ofthe heating type for illustrative purposes only. As illustrated in FIGS.1 through 4, the present invention is embodied in a combination controldevice having a hollow casing indicated generally at 10 and defining aninlet port 12 on one end adapted to be connected to a suitable fuelsupply such as a gas source (not shown) and a main outlet port 14 on anopposite end adapted to be connected with a main gas burner (not shown)by a suitable conduit. lnterposed in a passageway between inlet port 12and outlet port 14 is a main valve seat which is controlled by aflexible diaphragm defining a main valve member 16. The periphery of thediaphragm valve 16 is clamped between adjacent sections of the casing10, which are secured together as by cap screws (not shown). The maindiaphragm valve 16 separates a hollow cavity of the easing into an inletpressure chamber 1.8 and an operating pressure chamber 20. The diaphragmvalve 16 is spring biased against its valve seat and is controlled inoperation by the pressure differential between pressure chambers 18 and20 under the influence of a bleed flow passage (not shown) whichcommunicates with chamber 20.

The inlet pressure chamber 18 communicates with inlet 12 by means of atapered conical bore 22 which defines a seat for a rotatable plug valve24 having a sim ilarly tapered conical configuration. The centralportion of plug valve 24 is hollowed out and has an open bottom wallcommunicating with the inlet pressure chamber 18. Intermediate its ends,the tapered wall of plug valve 24 has an inlet bore 26 for selectiveregistry with an inlet passage 28 in the casing 10. An arcuate groove 30in the wall of plug valve 24 establishes communication between the inletpassage 28 and a pilot flow passage 32 which feeds a suitable pilotburner (not shown) through a pilot flow filter cavity, an outlet and asuitable conduit.

The large end of the plug valve 24 includes a hollow stem 34 in which anoperating shaft 36 is keyed for relative axial movement and for unitaryrotary movement therebetween. The shaft 36 also has a hollow portionseating a coil spring 38 that is mounted in compression between the stem34 and shaft 36. An annular shoulder 40 on the shaft 36'engages aninternal wall 42 in the casing to define the limit of axial movement ofthe shaft 36 by spring 38. The shaft 36 protrudes through the casing 10and has a manual operating dial or knob 44 fixed onto the end thereof.The undersurface of the dial 44 is partially recessed at 46 to receive astop member 48 on the casing 10 whereby the dial 44 may be only fullydepressed when it is in its pilot position as illustrated; when the dial44 is rotated to its off or on positions, the stop element 48 preventsfull depression of the dial 44.

Adjacent the manual dial 44, the casing 10 defines an internallythreaded aperture 50 in which a magnet housing 52 is fixedly supported.As is well known in the art, a thermal electromagnet in the housing 52is electrically connected to a thermocouple (not shown) to constitute asafety holding device. The thermocouple is conventionally disposedadjacent the pilot burner for the system and is responsive to a flamethereat to generate a thermoelectric voltage which feeds theelectromagnet in housing 52. The electromagnet in housing 52 includes anaxially movable armature 54 which protrudes out of the magnet housing 52interiorly of the casing 10 as shown. A coil spring 56 surrounds theprotruding portion of the armature 54 and is mounted in compressionbetween the wall of the housing 52 and a retainer washer 58 which issecured to the free end of armature 54.

One embodiment ofa dual lever mechanism in accordance with the presentinvention is illustrated in FIGS. 1 through 4 in various operativepositions with respect to the above-described combination control deviceand is indicated generally at 60. The dual lever mechanism 60 includes afirst lever 62 which is journaled for rotation about a pivot pin 64which is mounted for rotary movement in suitable apertures in the casing10. Lever 62 has a first arm 66 disposed in the path of axial movementof the annular shoulder 40 on the shaft 36 whereby depression thereof bythe dial 44 causes the lever 62 to pivot clockwise about pivot pin 64.Lever 62 includes second and third arms, of which the third arm 68 oflever 62 extends in the opposite direction of arm 66 for engaging themagnet armature 54 while the second arm 70 extends in substantiallyparallel spaced relation with arm 68 for movement into engagement with asecond lever 72. One end of lever 72 is bifurcated to accommodate lever62 and has a pair of upstanding mounting tabs 74 which are disposed oneach side of lever 62 and are journaled for rotation about pivot pin 64.A torsion spring 76 is coiled about pivot pin 64 and engages lever 72 ata first end and contacts a stop element 78 on casing 10 at its other endso as to bias lever 72 for clockwise rotation. The opposite end of lever72 carries a safety valve member 80 which seats against the wallsurrounding inlet passage 28.

In operation, FIG. 1 illustrates the dual lever assembly 60 in a firstor "closed position with plug valve 24 set to its pilot" position. Withvalve 80 closed, as shown, no gas can pass from inlet 12 to outlet port14 for supplying the main and pilot burners of the burner apparatus. Atthis time, spring 38 biases shaft 36 outwardly of casing 10 such thatannular shoulder 40 abuts internal wall 42 and is disengaged from arm 66of lever 62. With arm 66 disengaged, the high-rate spring 56 of housing52 acts through washer 58, the end of armature 54 and arm 68 of lever 62to rotate lever 62 counterclockwise whereupon the undersurface of arm 68engages lever 72 to rotate it counterclockwise thus closing valve 80against its seat. With lever 72 in its counterclockwise position,torsion spring 76 is wound-up such that it applies a force to lever 72which tends to rotate the lever in a clockwise direction. Opposing theforce of tension spring 76 is the force from high-rate spring 56, asnoted above, and the force of the gas pressure differential across valve80. Thus, the single force from torsion spring 76 tends to open valve80, while the combined forces of high-rate spring 56 and the gaspressure differential across valve 80 tend to close the valve.

When it is desired to ignite the pilot burner, knob 44 is rotated to itspilot position, as shown, such that recess 46 is aligned with protrusion48 on the casing to permit the knob and thus the shaft 36 to be manuallydepressed. As the shaft 36 moves inwardly of casing 10, shoulder 40 willengage arm 66 of lever 62 such that the lever will be rotated clockwiseas can be seen in FIG. 2. The initial movement of the shaft 36 (i.e.,approximately the first percent of its full downward travel) causeslever 62, acting through arm 68, to move armature 54 into housing 52almost to the point where the magnet poles thereof are seated againstthe magnet keeper within the housing. It is noted that a lever 62 isrotated from its counterclockwise position in FIG. 1 to that of FIG. 2,arm 68 moves away from the upper surface of lever 72 and, in view of thespaced relationship between arms 68 and 70, lever 72 becomes disengagedor freed from lever 62 and the force transmitted thereby from spring 56.Thus, in the position shown in FIG. 2, the forces acting upon lever 72are the biasing force from torsion spring 76 (which tends to open valveand the pressure differential across valve 80 (which tends to maintainthe valve closed). It should be noted that in FIG. 2 valve 80 is shownin the closed position indicating that the force exerted by the gaspressure differential across valve 80 in this illustration is sufficientto overcome the opening force of torsion spring 76 thus maintainingvalve 80 in this closed position. However, the gas pressure differentialacross valve 80 may not be sufficient to overcome the opening force oftorsion spring 76, in which case the lever 72 would follow lever 62 inits clockwise rotation around pin 64 although none of the resettingforce being applied to lever 62 would be transmitted to lever 72 at thistime.

Referring to FIG. 3, as the knob 44 is depressed to its full extent,lever 62 is further rotated clockwise to fully reset armature 54 againstthe magnet keeper in housing 52. At this point, lever 62 will have beenrotated sufficiently to bring arm 70 into engagement with theundersurface of lever 72 such that valve 80 is lifted slightly away fromits seat. With the valve-80 slightly opened, the gas pressuredifferential thereacross rapidly becomes balanced whereupon the onlyforce acting upon lever 72 is the clockwise biasing forceproduced bytorsion spring 76. Spring 76 thus acts to rotate lever 72 so as to swingvalve 80 to its fully open po sition as shown in FIG. 4.

The fully open position of valve 80 is defined by the engagement oflever 72 with the undersurface of arm 68 of lever 62 such that the valvedoes not swing up against an interior wall of the casing 10.

With valve 80 open, gas from inlet 12 flows through passage 28, groove30 in the wall of plug valve 24 and pilot flow passage 32 to the pilotburner (not shown) for ignition. Upon successful ignition of the pilotburner, the thermocouple sensor associated therewith will be heated soas to generate a thermoelectric voltagefor the reset magnet in housing52. This voltage causes the magnet to hold armature 54in its withdrawnposition shown in FIG. 4 whereupon levers 62 and 72 are maintained inthe position shown in FIG. 4 when shaft 36 returns to its normalposition after release of knob 44. Thereafter plug valve 24 may berotated to its on" position so as to bring bore 26 into registry withpassage 28 for establishing a main flow to the main burner (not shown)of the system.

If, at any time, the magnet in housing 52 becomes deenergized due topilot flame outage or any other cause, armature 54 will be released andspring 56 will cause the armature to move outwardly of the housing 52.As a result, both levers 62 and 72 will be rotated counterclockwisesimultaneously to their valve-closed positionsas shown in FIG. 1. Thereturn of levers 62 and 72 to the positions illustrated in FIG. 1winds-up torsion spring 76 and, as valve 80 becomes seated,reestablishes the gas pressure differential across valve 80 and cuts-offboth the pilot and main burner flows to safety shut-down the system andpreclude raw-fuel leakage.

The distinct advantages of the dual lever mechanism 60 according to thepresent invention can be readily appreciated in that lever 72, and thusvalve 80, is only moved by shaft 36 during approximately the lastpercent of movement thereof with such movement of lever 72 designed onlyto slightly lift valve 80 away from its seat thereby enabling balancingof the pressure differential thereacross. In other words, the opening ofvalve 80 is primarily produced by the action of torsion spring 76, andthe forces generated by manually moving knob 44 downwardly only act toslightly lift valve 80 from its seat to, in effect, release the valvefor subsequent movement by spring 76. At this same time, the full forcedeveloped by the movement of shaft 36 is transmitted to armature 54 soas to assure positive resetting thereof. In this manner, the holdingarmature will be efficiently reset while any possible damage to thelever 72 or the valve 80 is avoided regardless of the amount of forceapplied through knob 44 and shaft 36 during the reset cycle.

Referring now to FIGS. 5 and 6, a method of calibrating the dual levermechanism 60 of the subject invention is schematically illustrated suchthat compensation for variations in production tolerances may be readilymade. As shown in FIG. 5 one of levers 62 and 72 is bent so as to limitor decrease the amount of lost motion thercbetween, with arm 70 of lever62 shown in a typical bent or pre-calibrated position for illustrativepurposes only. With arm 70 bent, as shown, knob 44 is depressed and heldso as to bring the dual lever mechanism 60 to the position illustrated.With knob 44 maintained fully depressed, a calibration member 82 isinserted through inlet port 12 and the end thereof brought intoengagement with the distal end of lever 72 as shown in FIG. 6. A forceis then exerted through the calibration member to bring valve 80 closed,thus" bending arm to its proper calibrated position. It should beunderstood that the small amount of springback of arm 70 will besufficient to slightly lift the valve away from its seat to the positionillustrated in FIG. 3 during subsequent normal operation. The amount ofvalve opening due to the spring-back of arm 70 will primarily determinehow much the valve is opened by lever 62 during the reset cycle.

A modification of the dual lever mechanism of FIGS. 1-4 is illustratedin FIGS. 7-9, it being understood that such mechanism is adapted for usein various different applications and, in particular, may be effectivelyutilized in the combination control device described and illustratedabove with respect to FIGS. 14. For purposes of clarity, parts in FIGS.7-9 which are similar to parts in FIGS. 1-4 will be identified byidentical reference numerals with added thereto.

The dual lever mechanism of FIGS. 7-9 includes a first lever 162 whichis formed from a flat plate bent to provide a generally U-shapedconfiguration with a pair of side walls 184 and 186 interconnected by arear wall 188. A first arm 166 projects upwardly from the approximatecenter of the upper edge of rear wall 188. A lower central portion ofwall 188 is deformed out of the plane of wall 188 to provide a slightlyinclined offset second arm or operating surface 168 for lever 162, withthe undisturbed lower edges of wall 188 providing a third arm oroperating surface 170 as can be seen in FIG. 7. Each of the side walls184 and 186 of lever 162 defines an aperture and 187, respectively, toaccommodate a pivot pin 164 which may be press-fit therein, if desired,for retaining the assembly.

A second lever 172 having a generally U-shaped cross-section forstructural rigidity is also rotatably mounted on pin 164 by a pair ofupstanding, journaled tabs 174 formed on one end thereof. As can be seenin FIGS. 8 and 9, the width of lever 172 is slightly less than that oflever 162 such that lever 172 may be freely accommodated between walls184 and 186. The floor of lever 172 at its pivoted end defines a cut-outor void 190, with the floor of the lever adjacent each side of void slitlongitudinally and bent down to form a pair of arcuate tabs 192.Protruding from the floor of lever 172 into the throat of void 190 is anupwardly curved tongue 194 which is longitudinally crimped, asillustrated, for rigidification. Levers 162 and 172 are assembled on pin164 such that tongue 194 and tabs 192 cooperate with the rear surface ofarm or operating surface 168 and the lower edge of wall 188,respectively, to define the limits of rotation between the two levers. Atorsion spring 176 is coiled about pin '1 64 and has a first enddisposed in an aperture 196 in lever 172 and a second end which isadapted to engage protrusion or stop member 78 (see FIG. 1) of casing10.

The operation of the dual lever mechanism of FIGS. 7-9 is substantiallyidentical to that of the embodiment of FIGS. 14 and thus will not bedescribed again in detail for the sake of brevity. It is noted, however,that the dual lever mechanism of FIGS. 7-9 is adapted to be mounted incasing 10 in the same relative position as mechanism 60, with arm 166 oflever 162 adapted to be engaged by shoulder 40 of shaft 36 and with armor operating surface 168 engaging-armature 54. As illus trated in FIG.8, the undersurface of arm 168 of lever 162 engages tongue 194 of lever172 when the mechanism is in its valve closed position corresponding tothat illustrated in FIG. 1, and, as shown in FIG. 9, arm or surface 170of lever 162 engages tabs 192 of lever 172 when the mechanism is in aposition corresponding to that illustrated in FIG. 3.

The lever mechanism of FIGS. 7-9 may be calibrated in the same manner asis shown in FIGS. and 6 with the exception that tabs 192 of lever 172initially will be bent outwardly beyond their normal positions such thatas lever 162 is held in its clockwise position by shoulder 40 ofdepressed shaft 36 and lever 172 is forced so as to close valve 180 bymeans of calibration member 82, the tabs will be bent back to theirdesired positions.

Thus, it can be seen that the present invention provides a simple,inexpensive and reliable apparatus for enabling the sequential operationof two loads, namely a holding magnet and a safety valve member, by acommon operator such that any excessive force which might be applied tothe operator is isolated from damaging the safety valve member or thelever upon which it is carried. Furthermore, the present invention isreadily adaptable for use with many conventional control devices whichpresently utilize only a single lever mechanism thus enabling simplemodification of such controls so as to increase their safetycharacteristics while at the same time reducing maintenance and repaircost.

Inasmuch as the present invention is subject to many variations,modifications and changes in detail, it is intended that all mattercontained in the foregoing description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. In a gas control valve assembly having a safety valve member, aholding device, and a resetting operator therefor, the safety valvemember having open and closed positions and experiencing a pressuredifferential thereacross when in its closed position which acts tomaintain the valve member closed, a dual lever mechanism comprisingfirst lever means having a first arm engageable by the resettingoperator and a second arm,

second lever means carrying the safety valve member thereon for movementof the safety valve member between its open and closed positions, andmeans biasing said second lever means for movement of the safety valvemember to its open position,

said second lever means being disposed adjacent said first lever meansfor selective engagement of said second lever means by said second armof said first lever means after a preselected amount of lost motionbetween said first and second lever means whereby said first lever meansacts through said second lever means to lift slightly the safety valvemember from its closed position so as to release the pressuredifferential thereacross whereupon said second lever means moves thesafety valve member to its open position under the force of said biasingmeans thereby assuring opening of the safety valve member whileprecluding damage thereto by the action of the resetting operator.

2. The invention as recited in claim 1 wherein said first lever meansand said second lever means are rotatable about a common axis.

3. The invention as recited in claim 1 wherein said first lever means isintermediately pivoted, said first arm extends from one end thereof, andsaid second arm extends from an opposite end thereof, and wherein saidfirst lever means includes a third arm spaced from said second arm andextending in said opposite direction, said third arm engaging theholding device for actuation thereof.

1. In a gas control valve assembly having a safety valve member, a holding device, and a resetting operator therefor, the safety valve member having open and closed positions and experiencing a pressure differential thereacross when in its closed position which acts to maintain the valve member closed, a dual lever mechanism comprising first lever means having a first arm engageable by the resetting operator and a second arm, second lever means carrying the safety valve member thereon for movement of the safety valve member between its open and closed positions, and means biasing said second lever means for movement of the safety valve member to its open position, said second lever means being disposed adjacent said first lever means for selective engagement of said second lever means by said second arm of said first lever means after a preselected amount of lost motion between said first and second lever means whereby said first lever means acts through said second lever means to lift slightly the safety valve member from its closed position so as to release the pressure differential thereacross whereupon said second lever means moves the safety valve member to its open position under the force of said biasing means thereby assuring opening of the safety valve member while precluding damage thereto by the action of the resetting operator.
 2. The invention as recited in claim 1 wherein said first lever means and said second lever means are rotatable about a common axis.
 3. The invention as recited in claim 1 wherein said first lever means is intermediately pivoted, said first arm extends from one end thereof, and said second arm extends from an opposite end thereof, and wherein said first lever means includes a third arm spaced from said second arm and extending in said opposite direction, said third arm engaging the holding device for actuation thereof. 